1. Field of the Invention
The present invention relates to a magnetic tape cassette such as a video tape cassette.
2. Description of the Prior Art
FIG. 1 is a schematic view of the conventional magnetic tape cassette wherein reels (4), (5) holding a wound magnetic tape (3) are placed in the casing assembly comprising an upper half casing (1) and a lower half casing (2); tape guides (6), (7), (8) for guiding the magnetic tape (3) and a tape pad (9) etc. are placed in the running path of the magnetic tape (3) in the front of the casing between the reels (4), (5) so that the magnetic tape (3) can continuously run in contact with the tape guides (6), (7), (8) and the tape pad (9) to be wound on the reels; and a front cover (10) is mounted in the casing assembly so as to cover the front part of the casing assembly which provides a tape running plane for the magnetic tape (3). The front cover is used to protect the magnetic tape (3) and is usually secured through a locking means (not shown) and covers the magnetic tape (3) running in front of the casing assembly. When the casing assembly is fitted to the video deck set, the locking means is released to turn the cover over the upper half casing so that the running surface of the magnetic tape (3) is exposed to the front surface of the casing assembly; thus the cover is fitted to the upper half casing so as to be capable of opening and closing.
FIG. 2 is a schematic view showing an assembly of the upper half casing (1) and the front cover (10) wherein the front cover (10) is provided with supporting members (11), (12) projecting at both ends and pivot pins (13), (14) are provided on the supporting members (11), (12) so as to project inward at positions facing each other.
The front cover (10) can be mounted to the upper half casing as follows. A coil spring (15) is fitted to the pivot pin (13); the pivot pin (14) is loosely fitted into a hole (16) formed in the front side portion of the upper half casing, while the end portion (15a) of the coil spring (15) is brought into contact with the bottom surface of the upper half casing; thus the front cover is settled in the front portion of the upper half casing.
FIGS. 3A, 3B and 3C are schematic views showing an assembled structure of the upper half casing (1) and the front cover (10) in detail. In FIGS. 3A and 3B, a rectangular groove (17) is formed at the corner of the bottom surface of the upper half casing (1) corresponding to the position of the pivot pin (13) of the front cover (10) and a blade-like edge portion (18) is formed in front of the rectangular groove (17). The pivot pin (13) of the front cover (10) holds the coil spring (15) whose end portion (15) extends to engage with a recess (20) formed in the side wall portion (19) of the front cover (10) and the other end portion (15b) of the coil spring (15) is secured in the axial slit (13a) formed in the shaft (13) whereby the end portion (15a) of the coil spring (15) is brought into press-contact with the recess (20) by its spring action.
When the upper half casing (1) and the front cover (10) with the structures described above are combined together, the front cover (10) is moved in the direction P, as shown in FIGS. 3A and 3B, so that the front edge (18) of the upper half casing (1) is inserted between the end portion (15a) of the coil spring (15) and the side wall portion (19) to cause the end portion (15a) of the coil spring (15) to transfer from the recess (20) of the front cover (10) to the surface of the front edge (18) of the uper half casing (1) and finally, the end portion (15a) of the coil spring (15) settles in the rectangular groove (17) of the upper half casing.
The conventional magnetic tape cassette has no restricting means for preventing the side-shifting of the end portion (15a) caused when the end portion (15a) of the coil spring (15) is transferred from the front cover (10) to the rectangular groove (17). Accordingly, the end portion (15a) can not, sometimes, enter into the groove (17) and is deviated outside the groove (17) as shown by dotted line Q in FIG. 3C. The deviation of the coil spring (15) may cause a fault of the locking means (not shown) which prevents the opening of the front cover (10).